Trying to identify new customers -date created field and merging

We frequently get duplicate customer records (mainly because the website allows people to register as a new customer with an already existing email address, but that’s the topic of other threads…) 
We want to keep the most recent record when merging the duplicate records because it makes sense that that record would have the most up to date information.  However, using the most recent record as the Master creates the following problem:
The Date Created of the merged record becomes the date that the latest record was created.  We want it to be the date that the oldest record is created.  Anyway to do this and still have the other fields have the  data from the most recent record?  Date Created does not seem to be an editable field.  Having the Date Created equal the newest record instead of the oldest duplicate record creates problems when we run reports such as “New Customers this month” , where we use Date Created to determine the “new customers”.